NEW YORK (Reuters Health) - The concentration of biologic agents in the breast milk of women with inflammatory bowel disease (IBD) is minimal, with no increased risk of infections or developmental delays in breastfed infants out to 12 months, U.S. researchers report.

"Women with inflammatory bowel disease are understandably concerned about the safety of their medications during pregnancy and lactation, and their potential effects on their infants," said Dr. Rebecca Matro from Oregon Health & Science University in Portland.

"This study provides convincing data that breastfeeding while on biologics is low-risk," she told Reuters Health by email.

Dr. Matro and colleagues studied 824 women enrolled in the Pregnancy in Inflammatory Bowel Disease and Neonatal Outcomes (PIANO) registry, a multicenter national prospective study of pregnancy and neonatal outcomes in women with IBD and their infants, which was started in 2007.

The researchers collected 72 samples of breast milk from patients on biologic therapy 2013 to 2015, they note in Gastroenterology, online May 29. They assessed the concentration of biologic agents in breast milk at one, 12, 24 and 48 hours after dosing, and also at 72, 96, 120, and 168 hours from available samples.

All 824 women with treated or untreated IBD during pregnancy used the Ages and Stages Questionnaire 3 (ASQ3) to assess child development; 620 (75%) of the mothers breastfed and 204 (25%) did not. Mothers and pediatricians provided data on children's health and development.

The researchers reported detection of infliximab in breast milk samples from 19 of 29 treated women (max 0.74 mcg/mL); adalimumab in two of 21 treated women (max 0.71 mcg/mL); certolizumab in three of 13 treated women (max 0.29 mcg/mL); natalizumab in one of two treated women (max 0.46 mcg/mL); and ustekinumab in four of six treated women (max 1.57 g/mL). One woman who received golimumab had no detectable levels of the drug in her breast milk.

There were no significant differences in rates of infection or developmental milestones between infants whose mothers were on biologics, immunomodulators, or combination therapy and unexposed infants whose mothers were treated with mesalamines or steroids, or no medication. The rate of any infection was 39% vs. 39% (P=1.000), and the milestone score was 87 in exposed children versus 86 in controls (P=0.9992).

"This study is important and the first of its kind," said Dr. Miguel Regeuiro, chairman of the department of gastroenterology and hepatology at Cleveland Clinic in Cleveland, Ohio.

Dr. Regeuiro, who was not part of the study, told Reuters Health by email that the safety of biologics and immunosuppressive therapy during breastfeeding is a "question that is raised in our clinics all the time."

"The testing of breast milk was rigorous and outcome assessments for infection and milestone achievement were robust," he said, noting that the "data will inform gastroenterologists, pediatricians, and patients on the safety of continuing medications while breastfeeding."

According to Dr. Regueiro, "Breastfeeding has inherent health benefits for infants and should not be discouraged due to inflammatory bowel disease or medications."

Dr. Matro explained that, "Historically, women have been advised to avoid breastfeeding while on biologics or immunomodulators." But, she added, "mothers are more likely to flare if they stop their medications to breastfeed, which could result in greater harms to the mother's health and ability to care for the infant."